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ROUGHNESS OF TENNESSEE PAVEMENTS

A ROUGHOMETER TRAILER DEVELOPED BY THE BUREAU OF PUBLIC ROADS FOR MEASURING THE ROUGHNESS OF HIGHWAY PAVEMENTS WAS USED TO MEASURE SURFACE ROUGHNESS OF PAVEMENTS IN TENNESSEE. THE ROUGHOMETER TRAILER CONSISTS ESSENTIALLY OF A ROTATING WHEEL SUSPENDED FROM TWO LEAF SPRINGS WHICH ARE ATTACHED TO THE TRAILER FRAME WITH THE BOUNCING ACTION OF THE WHEEL BEING DAMPED BY TWO DASH POTS (SHOCK ABSORBERS). THE DASH POTS ARE FILLED WITH A FLUID OF FAIRLY CONSTANT VISCOSITY AND ARE CHECKED FOR FLUID LEVEL PRIOR TO EACH TEST TO INSURE CONSISTENT DAMPING ACTION SO THAT THE TEST RESULTS WILL BE UNIFORM. A WHEEL REVOLUTION COUNTER KEEPS THE EQUIPMENT OPERATOR INFORMED AS TO THE DISTANCE TRAVELED DURING A TEST. THE DEVICE USED TO MEASURE VERTICAL DEFLECTIONS OF THE TEST WHEEL IS A MECHANICAL INTEGRATOR WHICH SENDS AN IMPULSE TO AN ELECTRONIC DIGITAL COUNTER IN THE TOWING VEHICLE EACH TIME THERE IS A VERTICAL DEFLECTION OF 0.006 INCHES. A CABLE IS ATTACHED FROM THE INTEGRATOR TO THE TEST WHEEL TO MEASURE THE VERTICAL DEFLECTIONS. THE GENERAL SURVEY WAS COMPLETED IN THE LATTER PART OF 1964 AND INCLUDED APPROXIMATELY 155 MILES OF INTERSTATE PAVEMENT AND 127 MILES OF PAVEMENT IN THE PRIMARY HIGHWAY SYSTEM. STUDY RESULTS SHOW THAT: (1) THE GENERAL LEVEL OF ROUGHNESS OF HIGHWAYS IN THE PRIMARY SYSTEM HAS BEEN ESTABLISHED, (2) THE GENERAL LEVEL OF ROUGHNESS OF INTERSTATE HIGHWAYS HAS BEEN ESTABLISHED, (3) PRELIMINARY EVALUATIONS HAVE BEEN MADE OF RATE OF CHANGE IN PAVEMENT ROUGHNESS UNDER TRAFFIC, (4) SELECTED SECTIONS OF NEW CONSTRUCTION HAVE BEEN CHOSEN TO EVALUATE THEIR DEGREE OF ROUGHNESS, (5) INITIAL COMPARISONS OF THE RESULTS OF SURFACE ROUGHNESS AND PAVEMENT DEFLECTION TESTS HAVE BEEN MADE, (6) THE LEVEL OF ROUGHNESS OF BRIDGE DECKS HAS BEEN ESTABLISHED, AND (7) TESTS INDICATED THAT TO COMPLETELY EVALUATE A PAVING PROJECT THE ENTIRE LENGTH OF THE PROJECT MUST BE SURVEYED.